<?php
/**
 * Define a high level expression
 * 
 * <p>Sorry about the redundancy.
 *
 * @package junction.builder
 * @author Alexander Schearer <aas11@duke.edu>
 */
interface Expression_Expression {
	/**
	 * Evaluate the given expression
	 *
	 * @return String the result of evaluating the expression
	 */
	public function evaluate();
	
	/**
	 * Override the to string method to convert an expression to a string
	 *
	 * @return String a string representation of the expression
	 */
	public function __toString();
}
?>